What’s the Deepest hole we can possibly dig? By David Grossman.
The limiting factor is almost always the temperature. The Kola was abandoned in 1992 when workers hit 356 degrees Fahrenheit [180 degrees Celsius], far hotter than they had anticipated. The tunnel was eventually closed off in the early 2000’s. While there doesn’t seem to be much interest in getting lower — the Kola helped discover microscopic plankton, which is nice but hardly inspiring like space.